When talking about the AR-15 and the M-16, it is not uncommon to get the two confused.
After all, they both look alike, fire the exact same round, and have evolved over the
years with similar technologies.
But upon closer inspection, there are some very striking and glaring differences between
the two.
Most of these differences have been caused because of the missions these rifles were
designed to carry out.
After all, the M-16 was made at the height of the Cold War to give US troops a deadly
accurate, lightweight, and reliable rifle that could beat anything the Soviets could
manufacture.
On the other hand, the AR-15 was designed with customizability in mind to produce the
most accurate and fine-tuned civilian sharpshooting rifle on the market.
But how are these two related and where exactly do their paths converge?
To answer that question, one must go all the way back to the end of World War Two.
At the end of World War Two, each branch of the military conducted numerous studies on
how their service had performed during the war and where they could make technological
and tactical improvements.
One of those studies was conducted by the Army in assessing the effectiveness of their
primary rifle, the M-1 Garand.
The findings of the report were shocking.
On average, it was found that almost 80% of troops who had experienced combat had never
fired their weapon.
The study ultimately concluded that the reason why the average infantryman rarely, if ever,
actually fired his weapon in combat was his individual belief that his efforts of firing
a single shot at a time would not affect the outcome of the battle and felt outclassed
by larger weapons or an unseen enemy.
An interesting finding of the study was that those who carried the Browning Automatic Rifle,
or BAR, actually beat the statistic and these men fired more often than their rifle carrying
counterparts.
The conclusion was that these men had greater confidence in their ability to effect change
in the course of the battle and therefore fired more often.
They also found that soldiers who were near these men also fired their rifles more.
Therefore, Army officers concluded that soldiers in the future needed to be equipped with a
lightweight yet accurate rifle capable of fully automatic fire.
The first result of this was the M-14.
It was a very large rifle weighing in at almost ten pounds fully loaded with a 20 round magazine
of .308 ammunition.
It was capable of fully automatic fire and was the standard infantry rifle from the 1950s
through the first few years of the Vietnam war.
But soldiers in the field had many issues with it.
The rifle was unyielding and very heavy.
The heavy-caliber also limited the amount of ammunition that could be carried.
It was also uncontrollable in full automatic.
The Army needed something to replace it and began looking at other options even before
the Vietnam War started.
One of the earliest contenders to do so was an experimental rifle produced by the ArmaLite
company called the AR-10.
The AR-10 was a revolutionary rifle and was the brainchild of Eugene Stoner.
Stoner sought to develop a lightweight, accurate rifle that was reliable in all conditions
and could outperform all current rifles on the battlefield.
To do so, he developed several unique features that would later become ubiquitous with the
M-16, such as its patented gas blowback system, polymer design, and ergonomic build.
To market it to the military, he first chambered it in the standard 7.62x51 mm NATO round.
He did so because the military wanted to have their rifles and machine guns, which was the
M-60 machine gun at the time, chambered in the same round to reduce logistics issues.
Initial testing with the AR-10 was quite impressive to the military, but at the time of these
tests in the late 1950s, the government had already signed a huge contract for hundreds
of thousands of M-14 rifles.
Undeterred, Stoner went back to the drawing board to come up with a new design to ensure
that his rifle would be the one adopted by the military.
That new design was the AR-15.
The AR-15 was even better than his previous model and incorporated several major improvements.
To further decrease the weight, Stoner made the rifles from lighter polymers and plastics
in addition to using mostly aluminum parts wherever possible.
This reduced the weight by almost a third compared to the M-14.
Another major improvement was changing the caliber.
For the past several decades the military had been experimenting with smaller caliber
bullets that could still deliver the power of “full size” rounds like the .308 and
30-06 (pronounced thirty ought six) commonly used in machine guns.
The AR-15 model was the first to ditch the desire for a "full-sized" cartridge in favor
of a more compact and lighter, yet powerful round called the .223 Remington.
The benefits of using a smaller round took into consideration the years of study of wound
ballistics where heavier, higher velocity rounds simply passed through targets but smaller,
medium-sized rounds tumbled and caused wound cavitation- the expansion of pressure inside
a target- which caused more damage.
Medium-sized rounds like the .223 also enabled troops to carry more ammunition than before
and created less recoil, meaning more accurate shots and more controllable fully automatic
fire.
Stoner was eager to get his creation in front of the military and went to some unordinary
measures to do so.
At a Fourth of July celebration in 1960, he approached a high ranking general in the Air
Force and gave him an impromptu test demonstration.
Stoner set up a range of watermelon targets at 50, 100, and 150 yards and asked the general
to shoot them.
The general was so impressed by the rifle that he requested 100,000 on the spot.
This ambitious order was later revised to 8,500 a year later, but Stoner had just won
a huge step forward in marketing his rifle to the military.
Rigorous testing by the US Air Force and Army followed Stoner’s personal demonstrations
for top military brass.
All tests proved highly satisfactory and listed the rifle as highly reliable and accurate.
The Air Force was the first service to widely adopt the rifle in the early 1960s and once
Vietnam started to heat up the Army was soon to follow.
Within a few years, it was the main battle rifle of the US military in Vietnam through
today until its gradual replacement by the M4 Carbine.
Fundamentally, the M-16 and AR-15 are built and function the same.
The major components of both rifles are a lower and upper receiver, a barrel, front
and rear sights, a magazine well, a charging handle, a bolt assembly, a buttstock, a trigger
assembly, and a compensator.
The upper receiver carries the barrel and bolt assembly while the lower receiver houses
the trigger, firing mechanism, and magazine well.
These are connected to the rifle by Stoner’s iconic push pins first adopted in the 1960s.
How the rifle works is when a magazine is inserted into the magazine well, the first
round is put into the path of the bolt.
When the charging handle is cocked back, the bolt carrier assembly is now under pressure
and pushes the first round into the chamber when it is let go.
As the round is seated inside the chamber, the bolt assembly rotates and locks the bolt
into place.
Doing so prevents the unintended loss of gas pressures when the bullet is fired.
The round itself is fired when the trigger, which is attached to lugs that prevent the
hammer from going forward, is pulled.
The hammer then strikes the firing pin, which in turn hits the primer on the round.
The primer causes a small explosion that ignites the powder inside the cartridge sending the
bullet down the barrel.
After the round is fired, a small amount of gas enters what is called the gas tube at
the end of the barrel.
The hot, pressurized gases are then forced onto the bolt assembly.
When the pressure is great enough, which happens in fractions of a second, the whole bolt assembly
is forced rearward and a reverse process ensues.
As the bolt carrier travels backward, it unlocks and rotates what is called the extractor.
The extractor is the portion of the bolt carrier that pushes the spent casing out of the chamber.
The excess gases that were once pushing on the bolt carrier now push on the spent casing
as well and force it out of the extraction port.
When the bolt carrier travels backward, it also cocks the hammer again.
Basic physics tells us that every action has an equal and opposite reaction, so when the
gases stop pushing the bolt assembly slides forward.
Doing so pushes another round in the chamber and the rifle is ready to fire once again.
Since the design of the original M-16, there have been several variations to come out that
have improved on the initial model, whether for ironing out design flaws or adapting to
the needs of the US military.
The very first M-16- the one most similar to the AR-15 it was derived from- was the
M-16A1.
This model is the classic one that people recognize from all the shows and films about
the Vietnam War.
The next version to arise in the 1980s was the M-16A2.
This model came about when the military wanted to shift away from the “spray and pray”
mentality of fully automatic fire and instead focus on marksmanship.
Hence the major change with the M-16A2 was making it only semi-automatic or burst fire
capable.
The M-16A3 came out during the 1990s and briefly went back to the fully automatic mode of fire
of its predecessor.
However, as modern battlefields changed once more from the Cold War-style confrontations
of massed armies in small areas, to fighting smaller scale engagements over large distances,
the services adopted their final change to the M-16, the M-16A4.
The M-16A4 reverted back to the M-16A2 design of being capable of only semi-automatic and
three-round burst fire capability.
Another major change was the addition of a rail system on both the barrel and upper receiver.
By adding this rail system, the new design enabled advanced optical sights, lasers, and
flashlights to be added or exchanged with ease, thereby increasing the capability of
the average rifleman greater than ever before.
As far as raw data, the AR-15 and M-16A4 are close contenders.
The M-16A4 and AR-15 both weigh in at about seven pounds fully loaded.
The M-16A4 has an average effective range of 550 meters while the AR-15 lags behind,
with most firearms experts agreeing that the effective range for civilian shooters are
between 400-600 meters.
Both rifles are also manufactured standard with the .223 Remington round.
While the AR-15 and M-16A4 are both based on the same core design, there are a variety
of features, both functional and cosmetic, that would make one better than the other.
One of the main differences in AR-15s and M-16s is the closed third hole in the sear.
The sear is the portion of the rifle that determines what mode of fire it can shoot
in.
Most AR-15s have this third hole on the lower receiver that was a leftover from the M-16A1
design which enabled fully automatic fire.
Civilians could in theory drill a hole through it and make a few other modifications to make
it fire full auto, but doing so is a felony and highly illegal.
The M-16A4 by default has more firing options than civilian owned AR-15s.
Another critical design difference between the two is what is called the forward assist.
The forward assist is a button attached to a handle on the right side of the M-16A4 that
enables the shooter to manually push the bolt all the way forward to seat the round fully
in the chamber.
The feature was added by Stoner during the Vietnam War when reports from the field came
back that the rifles would jam incessantly.
While the root of the problem uncovered in a subsequent Congressional investigation found
that the cause of the jamming was the military using an improper propellant in their ammunition
that Stoner had warned them not to do, the forward assist has nonetheless remained an
integral feature of all further M-16 models.
That is because soldiers operate in some of the harshest environments in the world and
while they may clean their rifles frequently, dirt and debris are always quick to find a
home inside rifles, which makes the addition of a forward assist crucial to ensuring reliability.
AR-15s on the other hand do not come standard with a forward assist.
While some certainly do, there are no “standard” models of AR-15s like there are M-16A4s for
the military.
Civilian and police shooters face a more arduous task of clearing jams and malfunctions than
their military counterparts.
The AR-15 does have the advantage of customizability, especially with the mixing and matching of
uppers and lowers.
One of the benefits of this is allowing shooters to modify the caliber of their rifle from
the standard .223 up to a .50 caliber BMG or even down to pistol cartridges like the
.22 or 9mm.
While having the ability to change out calibers using different receivers does provide a lot
of versatility, it is not something that could be done in a firefight and is somewhat cost-prohibitive
both for the receiver and the often rare ammunition that is shot through them.
AR-15s also have the advantage of a wide range of magazines that can be used in the rifle,
including 100 round drum magazines, since the M-16A4 is only issued with the standard
30 round magazines the military has used for years.
M-16s do beat out AR-15s is another feature and that is the addition of the chrome-lined
barrel.
During the Vietnam War, it was discovered that by plating the inside of the barrel with
chrome, the life expectancy of the barrel could be increased and the amount of corrosion
decreased.
While the effect of chrome-lined barrels on accuracy is still a hotly debated topic, the
fact that they increase reliability is a proven concept.
AR-15s have the option of chrome-lined barrels but this feature is an additional cost for
the buyer and does not come standard in all AR-15s.
The last few differences between the two are merely cosmetic and demonstrate the military
utility of the M-16A4 over the AR-15.
The M-16A4 comes standard with a carrying handle while most AR-15s do not in favor of
extra space for rails to put scopes, sights, and other gadgets.
AR-15s usually do not come with a bayonet lug either and some do not have sling studs
to mount a sling which would make carrying long distances cumbersome and tiring.
In order to determine which one is better, it would really depend on what the rifles
were needed for.
If the user needed a rifle to arm a large group of people for combat, the M-16A4 would
definitely be the choice due to its increased reliability and standard configuration that
makes manufacturing, training, and employing large quantities of rifles both efficient
and at a lower cost.
If the user wanted the ability to customize and get the most out of the AR/M-16 platform,
the AR-15 would undoubtedly be the winner due to the wide range of calibers, gadgets,
barrels, and magazines that can be interchanged to produce the most effective rifle possible.
However, the capacity to equip large armies with this kind of setup is not likely due
to the small limited market of these calibers and high cost.
As for saying which one is better, it is best to say that the M-16A4 would outclass most
AR-15s in a battlefield environment but that the M-16A4 could be outclassed in the civilian
world say in a marksmanship competition due to the amount of customization that can be
done to it.